Linear alpha-olefins such as 1-hexene, 1-octene, and the like are used in a detergent, a lubricant, a plasticizer, and so on, and particularly, are widely used as a comonomer for adjusting the density of a polymer during the preparation of linear low density polyethylene (LLDPE).
Such linear alpha-olefins have been mostly prepared through a Shell higher olefin process. However, since the method synthesizes alpha-olefins of various lengths together according to Schultz-Flory distribution, there is an inconvenience of requiring an additional separation process in order to obtain a specific alpha-olefin.
In order to resolve these problems, a method of selectively synthesizing 1-hexene through a trimerization reaction of ethylene and a method of selectively synthesizing 1-octene through tetramerization of ethylene have been suggested. Further, various studies on catalyst systems enabling such selective oligomerization of ethylene have been undertaken.
However, the previously known catalyst systems have a problem in that the selectivity to 1-hexene, 1-octene or the like is not sufficient, or the catalytic activity for oligomerization is poor.